CEPT
ECC
Doc. SE19(13)ff
Electronic Communications Committee
61st meeting of PT SE 19
Copenhagen, Denmark, 7-8 January 2013
Date issued: 04th January 2013
Source:
Siae Microelettronica SpA
Subject:
Simulation of Urban Scenario (Symmetrical scenario)
Summary
This document presents the results of a planning simulation for the network under analysis (a
specific urban deployment agreed in SE19). The present simulation focuses on the more critical
radio nodes. The aim of this document is to carry out results of a interference analysis regarding
only the symmetrical planning scenario: it is possible to observe the same amont of saved
spectrum relative to asymmetric planning carried out by Ceragon
In addition few questions are posed to Ceragon study for better understanding the analysis
background.
1 Introduction
In the following figure the whole network under analysis is shown. Figure 2 shows the portion considered
by SIAE for the frequency plan: this portion is significative because it includes all the critical radio nodes.
The remaining links (not included in the present analysis) are links with a low level number (aggregation
level of the link, the last link connecting the tail site is aggregation 1), consequently, it is easy to perform a
frequency plan in order to assign them a correct TX/RX frequency channel without considering additional
spectrum.
Figure 1 Deployment topology
Figure 1 SIAE analysis topology
The parameters which were used in the planning of this network are the same considered by Ceragon in
their analysis. In particular:
- Availability objective: 99.995% for BER=10^-6;
- The fade margin used for the availability calculation includes the threshold degradation due to the
interference;
- Maximum threshold degradation is 3dB;
- Rain zone: K;
- Maximum antenna size: 3ft;
- Antennas type: class 3;
- Propagation model: ITU-R P.530-14 (the latest available model) for inland flat terrain, with pL=20% ;
- Presence of LOS between all sites (no losses due to terrain obstacles);
- Apply frequency reuse techniques as much as possible.
Data dimensioning:
- Capacity for aggregated link = Max (Peak capacity, NxBTM)
o Peak capacity = 130Mbps
o BTM = Busy Time Mean = 72Mbps
2 Frequency Plan Results
The present analysis is based on the following assumption:
 The capacity plan is the same shown in Ceragon study.
 The interference analysis has been carried out taking into account the constraints and
requirements specified in the previous section 1
 The TX power levels and antenna diameters have been not changed with respect to the Ceragon
analysis.
The following table shows the results of the interference analysis carried out for the network under study.
In particular, the low band portion has been considered: the same considerations could be carried out for
the high band.
Table 1: Results of frequency plan carried by SIAE
Not all links involved shown in figure 1 have been analysed in the present study: in particular, starting from
central node (site 33), all chains with two links have been considered. This topology presents, from the
frequency plan point of view, an exhaustive network layout: it is easy to find a suitable frequency channel
(in the already utilized spectrum portion) for links not involved in the present analysis because they need a
small portion of spectrum (less than 28MHz).
As shown in table 1, considering the frequency range used by Ceragon in their study (n°32 7MHz frequency
channel), only n°24 7MHz channel spectrum have been used and consequently n°8 7MHz channels have
been unused (the frequency range from 37226 MHz-37282MHz is unused). This result is comparable with
the performances due to use of asymmetrical planning as shown in Ceragon study.
In particular: This result has been reached considering a frequency reuse when possible.
As example (the most critical and significant case), in SIAE analysis links 33—42 and 33—18 use the same
56MHz frequency channel. This frequency plan fulfills the requirements shown in section 1. In fact,
considering link 33—18 as interfered link, the predominant interference power level is due to interfering
link 33—42 (-98dBm). This value is calculated taking into account the received power level received by the
interfered link (-32dBm according to Ceragon study) attenuated by the Front-to-back ratio of the antenna
in site 33 (66dBm).
The received interference power level (-98dBm) does not imply a C/I such as to cause a threshold
degradation more than 3 dB (the C/I value for 1 dB threshold degradation is around 33-34 dB).
3 Conclusions
Analysing the results of the frequency planning for the symmetrical scenario, the same portion of spectrum
has been saved with respect to the results carried out in the Ceragon study considering the asymmetrical
approach. SIAE BELIEVE that an obtimization is possible also for the asymmetrical frequency plan but the
improvement with respect the symmetrical scenario will be not so significative.
In SIAE opinion, the Ceragon study can be optimized with a “deeper” frequency reuse in order to save
spectrum. This approach allows the symmetrical scenario to decrease the difference in terms of saved
spectrum with respect to the asymmetrical approach.
We believe that the above partial analysis of the most significant part of the network is enough for
demonstrating the less evident difference between symmetric and asymmetric deployment. However, we
are open to recalculate in due time the whole network.
4 Further questions to the study
a)
b)
c)
The frequency selection for the 14, 28 and 56 MHz channels seems not aligned with the current
frequency arrangement (i.e. the centre frequencies are not taken from the recommendation raster.
Example U18-U33 UL has fo = 37135 MHz rather than 37142 MHz as in the raster).
Other examples can easily be identified.
TX/RX Duplex variation significantly large (see email correspondence)
The method for calculating the “required” and “actual” capacities is also to be clarified.
Note: Points a) and b) are not of particular important for the study itself but clarification and general
agreement on these factors are needed in view of possible changes in the channel arrangements.